1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel driven with a radio frequency, hereinafter referred to as “radio frequency PDP”, that is capable of lowering a discharge voltage and a method of fabricating the same. Also, the present invention is directed to a radio frequency PDP that is capable of preventing a cross talk between cells and a method of fabricating the same. Furthermore, the present invention is directed to a driving apparatus for the radio frequency PDP.
2. Description of the Related Art
Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. The PDP is largely classified into a direct current (DC) driving system and an alternating current (AC) driving system.
Since the AC-type PDP has an advantage of a low voltage driving and a long life in comparison to the DC-type PDP, it will be highlighted as the future display device. The AC-type PDP allows an alternating voltage signal to be applied between electrodes having dielectric layer therebetween to generate a discharge every half-period of the signal, thereby displaying a picture. Such an AC-type PDP uses a dielectric material that allows a wall charge to be accumulated on the surface thereof upon discharge.
Referring to FIG. 1 and FIG. 2, the AC-type PDP includes a front substrate 1 provided with a sustaining electrode pair 10, and a rear substrate 2 provided with address electrodes 4. The front substrate 1 and the rear substrate 2 are spaced in parallel to each other with having barrier ribs 3 therebetween. A mixture gas, such as Ne—Xe or He—Xe, etc., is injected into a discharge space defined by the front substrate 1, the rear substrate 2 and the barrier ribs 3. The sustaining electrode pair 10 makes a pair by two within a single of plasma discharge channel. Any one electrode of the sustaining electrode pair 10 is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode 4 while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrodes 10. Also, the sustaining electrode 10 adjacent to the sustaining electrode 10 used as the scanning/sustaining electrode is used as a common sustaining electrode to which a sustaining pulse is applied commonly. On the front substrate 1 provided with the sustaining electrodes 10, a dielectric layer 8 and a protective layer 9 are disposed. The dielectric layer 8 is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film 9 prevents a damage of the dielectric layer 8 caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 9 is usually made from MgO. The rear substrate 2 is provided with a dielectric thick film 6 covering the address electrodes 4. The barrier ribs 3 for dividing the discharge space are extended perpendicularly at the rear substrate 2. On the surfaces of the rear substrate 2 and the barrier ribs 3, a fluorescent material 5 excited by a vacuum ultraviolet lay to generate a visible light is provided.
In such an AC-type PDP, one frame consists of a number of sub-fields so as to realize gray levels by a combination of the sub-fields. For instance, when it is intended to realize 256 gray levels, one frame interval is time-divided into 8 sub-fields. Further, each of the 8 sub-fields is again divided into a reset interval, an address interval and a sustaining interval. The entire field is initialized in the reset interval. The cells on which a data is to be displayed are selected by a writing discharge in the address interval. The selected cells sustain the discharge in the sustaining interval. The sustaining interval is lengthened by an interval corresponding to 2n depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of first to eighth sub-fields increases at a ratio of 20, 21, 23, 24, 25, 26 and 27. To this end, the number of sustaining pulses generated in the sustaining interval also increases into 20, 21, 23, 24, 25, 26 and 27 depending on the sub-fields. The brightness and the chrominance of a displayed image are determined in accordance with a combination of the sub-fields.
In the AC-type PDP, a sustaining pulse having a duty ratio of 1, a frequency of 200 to 30 kHz and a pulse width of 10 to 20 μs is alternately applied to the sustaining electrode pair 10. The sustaining discharge occurring between the sustaining electrode pair 10 in response to the sustaining pulse is generated only once at an extremely short instance. Charged particles produced by the sustaining discharge moves through a discharge path between the sustaining electrode pair 10 in accordance with the polarity of the sustaining electrode pair 10 to be accumulated on an upper dielectric layer 14 and thus be left into a wall charge. This wall charge lowers a driving voltage during the next sustaining discharge, but it reduces an electric field at a discharge space during the corresponding sustaining discharge. Thus, if a wall charge is formed during the sustaining discharge, then a discharge is stopped. As mentioned above, the sustaining discharge is generated only once at a much shorter instance than a width of the sustaining pulse, the majority of sustaining discharge time is wasted for a preparation step for the wall charge formation and the next sustaining discharge. For this reason, since the conventional AC-type PDP has a much shorter real discharge interval than the entire discharge interval, it has a low brightness and low discharge efficiency.
In order to solve the above-mentioned low brightness and discharge efficiency problem in the AC-type PDP, there has been suggested a radio frequency PDP, hereinafter referred to as “RFPDP”, for exploiting a radio frequency signal of tens of to hundreds of MHz to cause the sustaining discharge. In the RFPDP, electrons make a vibrating motion within the cell by the radio frequency discharge.
Referring now to FIG. 2, the RFPDP includes a rear substrate 12 formed in such a manner that an address electrode 14 is perpendicular to a scanning electrode 18, and a front substrate 30 formed in such a manner that a radio frequency electrode 28 is parallel to the scanning electrode 18. Between the address electrode 14 and the scanning electrode 18, a first lower dielectric layer 16 for insulation between these electrodes is provided. A second lower dielectric layer 20 and a protective film 22 are disposed on the scanning electrode 18. A lattice-shaped barrier rib 24 is formed on the protective film 22. The surface of the lattice-shaped barrier rib 24 is coated with a florescent material 26. An upper dielectric layer 29 is formed evenly on the front substrate 30 provided with a radio frequency electrode 28.
The RFPDP displays a picture by a combination of a number of sub-fields, each of which includes a reset interval, an address interval and a sustaining interval. In the reset interval, the entire field is initialized. Next, in the address interval, a data pulse and a scanning pulse are applied to the address electrode 14 and the scanning electrode 18, respectively, to select cells by a discharge between the address electrode 14 and the scanning electrode 18. The selected cells display a picture by the vibration motion of electrons in the sustaining interval. At this time, a radio frequency signal of several to tens of MHz is applied to the radio frequency electrode 28, and a radio frequency of direct current bias voltage is applied to the scanning electrode 18. By this radio frequency signal, electrons within the cells make a vibration motion within the discharge space in accordance with the polarity of the radio frequency signal. The vibration motion of electrons successively ionizes a discharge gas. A vacuum ultraviolet ray generated by such a discharge excites a fluorescent material 26 to generate a visible light upon transition of the fluorescent material 26. As described above, the RFPDP exploits a radio frequency signal to cause a discharge continuously during the sustaining interval, so that it can obtain higher brightness and higher discharge efficiency in comparison to the AC-type PDP.
However, the conventional RFPDP has a problem in that, since the address electrode 14 and the scanning electrode 18 are positioned at a different height with having dielectric layers 16 and 20 therebetween and the dielectric layers 16 and 20 have a large thickness as shown in FIG. 3, a large voltage drop is caused by the dielectric layers 16 and 20 existing in a discharge path 32 during the writing discharge. In other words, a writing voltage applied to the address electrode 14 and the scanning electrode 18 is lowered as much as a magnitude of the voltage drop caused by the thickness of the dielectric layers 16 and 20. As a result, there can occur an unstable writing discharge. If a writing voltage is raised so as to stabilize the writing discharge, then a discharge field generated upon writing discharge is diffused to the adjacent cells along the address electrode 14 or the scanning electrode 18 to cause a cross talk between the cells. The generation of a cross talk between the cells causes a miss discharge. Also, if a writing voltage is raised, then the manufacturing cost and the power consumption increase because a driving circuit is implemented with the high voltage circuit devices.